GB2529870A

GB2529870A - Vehicle suspension system

Info

Publication number: GB2529870A
Application number: GB1415713.5A
Authority: GB
Inventors: Mark Mansfield; Andrew Elliot; Adam Dickens
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2014-09-05
Filing date: 2014-09-05
Publication date: 2016-03-09
Anticipated expiration: 2034-09-05
Also published as: GB2529870B; GB201415713D0

Abstract

A vehicle suspension system is described that comprises a control arm 16 mounted at a first end 20 to a frame portion 32 of a vehicle. At least a portion of the control arm is arranged to slide relative to the frame portion when the control arm is subjected to loads exceeding a predetermined level. The system includes retaining means 50 configured to prevent the control arm from sliding relative to the frame portion when the control arm is subjected to loads below the predetermined level. A sliding motion of the control arm may result in an angular displacement of a steering wheel to warn a driver of potential damage to the suspension system. The frame portion may be a clevis and the retaining means a nut and bolt assembly 54 fastening the control arm to the clevis. The retaining means may also be a deformable component such as a washer and tab assembly (70 fig.9) or a plate (80 fig.10) arranged flush with the frame member and comprising a further slot (82) to retain one or more fasteners (84).

Description

VEHICLE SUSPENSION SYSTEM

TECHNICAL FIELD

The present disclosure relates to a suspension system for a vehicle and to a vehicle including a suspension system.

BACKGROUND

High load events such as a vehicle striking a kerb or pothole can result in damage to the vehicle suspension components such as the ball joints or control arms. The ball joints are the connection between the control arms of the vehicle suspension system and the steering knuckle, which connects the wheel hub to the suspension system. Damaged ball joints, for example, may initially go undetected by the driver as in many cases they produce no discernible symptoms. However, damage to the ball joints can result in the ball joints failing due to fatigue. Failure of a ball joint can render the vehice inoperable until such time as the ball joint and any other vehicle components damaged as a result of the failure are repaired.

In a multilink front suspension system having compression and lateral lower control arms, it is known in the prior art to make one of the arms collapsible by provision of a kink in the arm. For example, the kinked arm may be designed to collapse upon high sideways loading to absorb loads in the event of a side impact. The collapsed control arm must be replaced during repair of the suspension system, and in some cases the collapsed control arm may render the vehicle un-driveable until such time as the suspension system has been repaired. Replacement of the collapsed control arm and repair of the suspension system is expensive and it is inconvenient if the vehicle is un-driveable in the meantime.

Against this background it is an object cf the present invention to provide an improved suspension system that overcomes one or more of these disadvantages of prior art suspension systems.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided a vehice suspension system comprising a control arm mounted at a first end to a frame portion of a vehicle, wherein at least a portion of the control arm is arranged to slide relative to the frame portion when the control arm is subjected to loads exceeding a predetermined level, the system further comprising retaining means configured to prevent the control arm from sliding relative to the frame portion when the control arm is subjected to loads below the predetermined level.

When the suspension system is subject to a high load event, for example if the vehicle hits a kerb or pothole at speed or when braking, the control arm slides relative to the frame portion of the vehicle. In an embodiment of the invention, the system is configured such that loads in excess of approximately 60 kN cause the control arm to slide. As the control arm slides, it absorbs some of the impact of the high load event, and thus protects other components of the vehicle and suspension system from damage. For example, the novel and inventive sliding arrangement of the present invention serves to protect the ball joints from sustaining damage. Furthermore, by sliding, the control arm itself is less likely to break or become damaged during high load events, thus reducing repair costs.

In a particularly advantageous arrangement of the present invention, when the control arm slides, it causes a permanent anguar displacement of the steering wheel of the vehicle. This is an immediate signal to the driver that the vehicle requires attention following a high load event. However, the vehicle advantageously remains driveable after the event, and with substantially no negative effect on the control of the vehicle, so the driver can safely drive the vehicle to a service station to be checked and repaired. This is an advantage over collapsible suspension arrangements which could render the vehicle inoperable after a high load event.

The system may be configured to cause a permanent angular displacement of the steering wheel of between 5 to 15 degrees. The angular displacement maybe between 7 to 12 degrees. The inventors of the present invention have determined that an angular displacement of seven degrees or more is readily noticed by the driver. The angular displacement should be minimised, whilst remaining noticeable, in order not to adversely affect the control of the vehicle. The inventors have determined that an angular displacement of 12 degrees is a suitable upper limit whereby the driver's control over the vehicle is not substantially affected.

Upon servicing the suspension system, critical components such as the ball joints may be checked for damage and replaced or repaired if necessary and the sliding arrangement between the control arm and the frame portion can be reset to the factory setting. In contrast to prior art suspension arrangements where high impact events may cause no discernible symptoms at first but may later cause a fatigue failure, the present inventon may advantageously cause a benign fault (for example misalignment of the steering wheel), which signals to the driver that the vehicle requires specialist attention.

Subsequent fatigue failures may therefore be substantially avoided as a result of the present invention.

According to another aspect of the invention, there is provided a vehicle comprising the vehicle suspension system as set out in the previous aspect.

A second end of the control arm could be mounted directly or indirectly to a knuckle, e.g. a steering knuckle. The control arm may be configured to slide relative to the frame portion in a sliding direction generally parallel to an axis defined by a straight line extending between the first and second ends of the control arm. The control arm may be straight, in which case the axis may extend along a body of the control arm, or the control arm may be curved, for example a so-called banana arm'.

In an embodiment of the present invention, the first end at the control arm is slidably mounted to the frame portion of the vehicle. The first end of the control arm may be pivotaNy connected to the frame portion, for example via a bushing, such that the control arm is able to pivot relative to the frame portion about a pivot axis. The sliding motion between the control arm and the frame portion may cause a displacement of the pivot axis in a sliding direction.

The frame portion of the vehicle may comprise a slot through which the first end of the control arm is connected to the frame portion. The control arm may be arranged to slide along the slot when subjected to a load exceeding the predetermined level. The frame portion may comprise a pair of opposed slots. The first end of the control arm may be connected between the pair of slots and be slidable along the pair of slots when subjected to a load exceeding the predetermined level. The frame portion could be a

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clevis and the slots are provided respectively in mutually-opposed side walls of the clevis.

The retaining means may be configured to exert a clamping force between the control arm and the frame portion. The clamping force could be sufficient to prevent the control arm from sliding relative to the frame portion when the control arm is subjected to loads below the predetermined level, but insufficient to prevent the control arm from sliding relative to the frame when the control arm is subjected to loads exceeding the predetermined level. In an embodiment of the invention, the retaining means comprises a nut and bolt assembly.

The retaining means may comprise a deformable component configured to deform when the control arm is subjected to loads above the predetermined level. For example, the retaining device may comprise a washer having a tab extending from its periphery. The tab may be bent and engages with a locating feature defined in the frame portion adjacent the slot. The tab may be configured to straighten when the control arm is subjected to loads exceeding the predetermined level thereby permitting the control arm to slide along the slot(s).

In a particular embodiment, the retaining device comprises a plate arranged flush with the frame portion. The plate has an aperture through which the bolt extends, and the plate further comprising a slot extending substantially parallel to the slot defined in the frame portion. The plate may be clamped to the frame portion via one or more fasteners located in the slot in the plate. In a particular example these fasteners are rivets and serve to connect the plate in a predetermined position relative to the vehicle frame.

Accordingly, the plate provides a convenient locating device that enables the control arm to be correctly positioned in the slot(s) in the frame portion when the suspension system is initially set or when it is reset after a high load event.

The suspension system could be for a front wheel of the vehicle. In an embodiment the control arm is a front lower control arm. The suspension system may be a multilink suspension system and the control arm may be a compression arm.

The inventive concept encompasses a vehicle comprising the suspension system described above.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a front view of a front sub-frame of a vehicle to which a front suspension system according to an embodiment of the present invention is mounted; Figure 2 is a bottom view of the front sub-frame of Figure 1; Figure 3 is a perspective view of first and second lower control arms of the suspension system according to an embodiment of the present invention, in which an end of the first control arm is slidably mounted to a clevis portion of the front sub-frame; Figure 4 is a close-up perspective view of the clevis portion of the front sub-frame prior to attaching the first control arm and showing a pair of slots provided in the side-walls of the clevis portion; Figure 4A is a schematic representation of one of the slots, which illustrates the shape and size of the slot; Figure 5 is a close-up perspective view of the clevis with the control arm attached; Figure 6 is a cross-sectional plan view of the clevis and attached first control arm; Figure 7 is a side view of the clevis and the attached first control arm, indicating the direction in which the control arm is slidable relative to the sub-frame; Figure 8 is a plan view of the clevis and the attached first control arm, indicating the direction in which the control arm is slidable relative to the sub-frame; Figure 9 is a perspective view of a further embodiment of the present invention in which the system further comprises a deformable tab washer; and Figure 10 is a perspective view of yet another embodiment of the present invention in which the system further comprises a pressed plate attached to the clevis by rivets.

DETAILED DESCRIPTION

Referring to Figure 1, this shows a front sub-frame 10 of a vehicle (in this case a car) as viewed from the front. A front-left wheel 1 2a and a front-right wheel 1 2b are located adjacent to the sub-frame 10. Each wheel 12a, 12b is mounted to the sub-frame 10 via an associated front suspension system 14 according to an embodiment of the present inventon.

Referring now to the bottom view of Figure 2, the front suspension system 14 in this example is a multilink suspension system comprising first and second lower control arms 16, 18. The first control arm 16 is also referred to herein as the compression arm', and has a generally curved shape. This arm iSis sometimes referred to as a banana arm' in view of its curved shape. The second arm 18 is also referred to herein as the lateral arm! and is generally straight and extends in a lateral (i.e. width wise) direction between the associated wheel 12a, 12b and the sub-frame 10. The control arms 16, 18 are each connected at a first end 19, 20 to the sub-frame 10 and at a second end 21, 22 to a steering knuckle, to which the wheels 12a, 12b are mounted. The steering knuckles are obscured by the wheels 12a, 12b in Figure 2.

A dashed line 24 extending between the first and second ends 20, 22 of the compression arm 16 is shown on Figure 2, and the significance of this line will be explained later.

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Referring now to the perspective view of Figure 3, this shows the first and second control arms 16, 18 of the suspension system 14 for the front-left wheel 12a. The lateral arm 18 is connected at its first end 19 to the sub-frame 10 via a rubber bushing 26, which allows the lateral arm 18 to pivot up and down relative to the sub-frame 10. The second end 21 of the lateral arm 18 comprises a ball jont 28, which connects to the steering knuckle.

The second end 22 of the compression arm 16 also connects to the second end 21 of the lateral arm 18 via a rubber bushing 30, which allows the compression arm 16 to pivot relative to the lateral arm 18. Hence the compression arm 16 is indirectly connected to the steering knuckle in this example. The first end 20 of the compression arm 16 is connected to a clevis portion 32 of the sub-frame 10 via a rubber bushing 34 (visible in Figure 6), which allows the compression arm 16 to pivot up and down relative to the sub-frame 10 about a pivot axis 36.

Referring now to Figure 4, the clevis portion or frame portion 32 of the sub-frame 10 comprises a pair of mutually opposed and spaced-apart side walls 38a, 38b defining a gap 40 in between. A slot 42a, 42b is provided in each of these side walls 38a, 38b. The slots 42a, 42b are in the form of elongate apertures which extend completely through the thickness of the side walls 38a, 38b of the clevis 32. The slots 42a, 42b are arranged opposite one another in the respective side walls 38a, 38b of the clevis 32. Referring to Figure 4A, this shows the shape and size of the slots 42a, 42b. The slots 42a, 42b have rounded first and second ends 44, 45 which are part circular. The length of the slots in this example is 28 millimetres between the centres of the circles 46 defining the respective part-circular ends 44, 45 of the slots 42a, 42b, as shown by the double-headed arrow 48 in Figure 4A.

Referring now to Figure 5, this shows the first end 20 of the compression arm 16 attached to the clevis portion 32 of the sub-frame 10. The first end 20 of the compression arm 16 is located in the gap 40 defined between the opposed side walls 38a, 38b of the clevis 32. A fastener 50 in the form of a nut 52 (shown in Figure 6) and bolt 54 is used to attach the compression arm 16 to the clevis 32. Referring also to the cross-sectional view of Figure 6, the bolt 54 extends through the pair of opposed slots 42a, 42b defined in the respective side walls 38a, 38b of the clevis 32, and through a central bore 56 defined in the rubber bushing 34 of the compression arm 16. The pivot axis 36 between the control arm 16 and the clevis 32 is defined by the longitudinal extension of the bolt 54 and is shown by the horizontal dashed-dot line in Figure 6. The nut 52 is provided on a threaded end 58 of the bolt 54 and a first washer 60 is provided between the nut 52 and an outer surface 62b of a second side wall 38b of the clevis 32. A second washer 64 is provided between a head 66 of the bolt 54 and an outer surface 62a of a first side wall 38a of the clevis 32.

When the compression arm 16 is initially attached to the clevis 32, the bolt 54 is located at a first position in the slots 42a, 42b, which in this example is at the first ends 44 of the slots 42a, 42b, as shown in Figure 5. The nut 52 is tightened to clamp the compression arm 16 to the sub-frame 10, i.e. to clamp the first end 20 of the compression arm 16 between the opposed side walls 38a, 38b of the clevis 32. Referring again to Figure 6, the bushing 34 allows the compression arm 16 to pivot up and down relative to the clevis 32 when the nut 52 is tightened. The nut 52 is tightened to a predetermined torque level which prevents the compression arm 16 from sliding in the slots 42a, 42b when the suspension system 14 is subjected to normal load levels. In this example the torque level is approximately 200 Nm. Normal load levels are levels that do not generally cause damage to the suspension components. Hence, under normal load levels the bolt 54 remains at the first ends 44 of the slots 42a, 42b as shown in FigureS.

In the event that the suspension is subjected to a high load event, for example if the vehicle hits a kerb or pothole, then the force of the impact may be sufficient to overcome the clamping force of the nut and bolt fastener 50. II this occurs, then the first end 20 of the compression arm 16 slides along the slots 42a, 42b towards a second position at the second ends 45 of the slots. In this example, loads in excess of approximately 60 kN will cause the compression arm 16 to slide along the slots 42a, 42b. Referring to the side view of Figure 7, this shows the first end 20 of the compression arm 16 in the first position along the slots 42a, 42b, and the arrow 68 indicates the direction of sliding in a high load event.

Likewise in the plan view of Figure 8, the arrow 68 indicates the direction of sliding in a high load event. Here it can be seen that sliding motion of the control arm 16 relative to the sub-frame 10 causes displacement of the pivot axis 36 in the sliding direction 68.

Referring also again to Figure 2, the sliding direction 68 is generally parallel to the dashed line 24 in Figure 2, which is the straight line extending between the first and second ends 20, 22 of the compression arm 16.

In prior art systems, which do not incorporate a sliding connection between the control arms and the sub-frame, such a high load event may cause the control arm to break or buckle or cause damage to the ball joints for example. However, the sliding arrangement of the present invention is able to absorb some of the impact of a high load event, which advantageously protects the ball joints and the control arms from becoming damaged in such events.

When the control arm 16 slides to the second position, this results in a permanent angular displacement of approximately seven degrees in the steering wheel of the vehicle. This is an immediate sign to the driver that the vehicle requires attention. The vehicle is still drivable, which allows the driver to drive the vehicle to a service centre rather than the vehicle requiring recovery. During service, the ball joints 28 (Figure 3) and other suspension components can be examined and replaced or repaired if required.

The sliding connection between the compression arm 16 and the clevis 38 is also reset by positioning the compression arm 16 at the first position in the slots 42a, 42b and re-tightening the nut 52 (Figure 6) to the predetermined torque level.

The present invention represents a significant advantage over prior art systems where damage to the suspension components may go undetected as there may be no symptoms of damage after a high load event. Such prior art systems therefore are more vulnerable to fatigue failures, which can be dangerous and leave the vehicle inoperable and requiring recovery. The offset steerng wheel provides an immediate visual indication to the driver that the vehicle requires attention, and hence the suspension can be assessed to check whether any of the components are damaged. The driver will also be able to feel the effects of the offset steering through the wheel. By absorbing impact in the sliding mechanism, the suspension components are less likely to incur damage in high load events with the present invention and hence repair costs are reduced.

Referring to Figure 9, this shows a further embodiment of the present invention. The further embodiment is otherwise identical to the other embodiment, but includes an additional metal tab washer 70 having an annular body 72 with a tab 74 protruding from its outer periphery. Also, it will be appreciated that Figure 9 shows the bolt 54 extending in the reverse direction compared to the other embodiment, i.e. so that the nut 52 is adjacent to the first side wall 38a of the clevis 32, although it should be appreciated that the orientation of the bolt 54 in all embodiments is interchangeable.

In this embodiment, the first side wall 38a of the clevis 32 also includes an aperture 76 adjacent the slot 42a. The tab washer 70 is provided between the nut 52 and the outer surface 62a of the first side wall 38a of the clevis 32. A further washer 64 is provided between the tab washer 70 and the nut 52. The tab washer 70 has a first configuration in which the tab 74 is bent and extends through the aperture 76 adjacent the slot 42a. As shown in Figure 9, the bent tab 74 forms a hook that hooks around the first side wall 38a of the clevis 32 in the aperture 76. The tab washer 70 conveniently serves to locate the bolt 54 correctly in the first position when the suspension system 14 is set in the factory or during servicing. A similar tab washer may be provided on the other side of the clevis, i.e. between the bolt head and the outer surface of the second side wall of the clevis.

The tab 74 is a detormable and is configured to deform such that it straightens when the suspension system 14 is subjected to a load exceeding a predetermined evel (i.e. a high load event). The straightened tab permits the first end of the compression arm 16 to slide in the slots 42a, 42b as described above in relation to the other embodiment. The straightened tab is also referred to as a second configuration' of the tab 74. When subjected to loads below the predetermned level, the tab 74 remains in the bent first configuration and additionally allows the tab washer 70 to act as a retaining means by serving to retain the compression arm 16 in the first position with respect to the slots 42a, 42b and thus preventing sliding of the arm 16 relative to the sub-frame 10. The tab washer 70 is an optional feature as the nut 52 and bolt 54 can provide sufficient clamping force to prevent sliding under normal conditions (i.e. the other embodiment). However, as well as providing a convenient locating feature, the tab washer 70 can provide an additional safe guard to prevent sliding under normal loads or to allow lower torque levels to be applied to the nut 52. The tab washer 70 will require replacing during repair/resetting of the suspension system 14.

Referring now to Figure 10, this shows a yet another embodiment of the present inventon in which a pressed metal plate 80 is provided between the nut 52 and the first side wall 38a of the clevis 32. Again, a further washer 64 is provided between the nut 52 and the pressed plate 80. The pressed plate 80 includes a slot 82 extendng parallel to the slot 42a in the side wall 38a of the clevis 32. The pressed plate 80 is riveted to the side wall 38a of the clevis 32 by first and second rivets 84a, 84b, which extend through apertures in the side wall 38a and through the slot 82 in the plate 80. The rivets 84a, 84b in combination with the nut and bolt act as retaining means, only allowing the compression arm 16 to slide in the slot 82 when a load exceeding predetermined level is applied. Again, a similar plate may be provided on the other side of the clevis 32. The plate(s) 80 provide a convenient locating feature allowing the bolt 54 to be correctly set in a first position when the suspension is assembled, adjusted or repaired.

Many modifications may be made to the above examples without departing from the scope of the invention as defined in the accompanying claims. For example, rather than providing slots that extend through the entire thickness of the clevis, the clevis may be provided with suitable grooves extending along the inner surfaces of the opposed side walls, and instead of a nut and bolt assembly, the control arm could be attached to the grooves by a rod that engages at each end with one of the grooves. The rod may be a spring bar biased towards an extended configuration, similar to a watch strap pin, albeit more robust. Accordingly, it will be appreciated that neither the slots nor the nut and bolt assembly are essential elements of the invention and other alternative arrangements are possible. Whilst embodiments shown in the figures include a sliding connection between the control arm and the sub-frame, in other embodiments the control arm may have two sections joined by a sliding linkage.

Further aspects of the present invention are set out in the following numbered clauses: Clause 1. A vehicle suspension system comprising a control arm mounted at a first end to a frame portion of a vehicle, wherein at least a portion of the control arm is arranged to slide relative to the frame portion when the control arm is subjected to loads exceeding a predetermined level, the system further comprising a retaining device configured to prevent the control arm from sliding relative to the frame portion when the control arm is subjected to loads below the predetermned level.

Clause 2. The vehicle suspension system of Clause 1, wherein the suspension system is configured such that sliding motion of the control arm causes an angular displacement of a steering wheel of the vehicle.

Clause 3. The vehicle suspension system of Clause 1, wherein a second end of the control arm is mounted directly or indirectly to a knuckle, and the control arm is configured to slide relative to the frame portion in a sliding direction generally parallel to an axis defined by a straight line extending between the first and second ends of the control arm.

Clause 4. The vehicle suspension system of Clause 1, wherein the first end of the control arm is slidably mounted to the frame portion of the vehicle.

Clause 5. The vehicle suspension system of Clause 1, wherein the first end of the control arm is pivotally connected to the frame portion such that the control arm is able to pivot relative to the frame portion about a pivot axis.

Clause 6. The vehicle suspension system of Clause 5, wherein sliding motion between the control arm and the frame portion causes displacement of the pivot axis in a sliding direction.

Clause 7. The vehicle suspension system of Clause 1, wherein the frame portion comprises a slot through which the first end of the control arm is connected to the frame portion and wherein the control arm is arranged to slide along the slot when subjected to a load exceeding the predetermined level.

Clause 8. The vehicle suspension system of Clause 7, wherein the frame portion comprises a pair of opposed slots and the first end of the control arm is connected between the pair of slots and is slidable along the pair of slots when subjected to a load exceeding the predetermined level.

Clause 9. The vehicle suspension system of Clause 8, wherein the frame portion is a clevis and the slots are provided respectively in mutually-opposed side walls of the clevis.

Clause 10. The vehicle suspension system of Clause 1, wherein the retaining device exerts a clamping force between the control arm and the frame portion, the clamping force being sufficient to prevent the control arm from sliding relative to the frame portion when the control arm is subjected to loads below the predetermined level, and the clamping force being insufficient to prevent the control arm from sliding relative to the frame when the control arm is subjected to loads exceeding the predetermined level.

Clause 11. The vehicle suspension system of Clause 1, wherein the retaining device comprises a nut and bolt assembly.

Clause 12. The vehicle suspension system of Clause 11, wherein the retaining device comprises a deformable component configured to deform when the control arm is subjected to loads above the predetermined level.

Clause 13. The vehicle suspension system of Clause 12, wherein the control arm is connected to the frame portion via a nut and bolt assembly, the bolt extending through the first end of the control arm and through a slot defined in the frame portion, and wherein the retaining device comprises a washer having a tab extending from its periphery, the tab being bent and engaging a locating feature defined in the frame portion adjacent the slot, and wherein the tab is configured to straighten when the control arm is subjected to loads exceeding the predetermined level thereby permitting the control arm to slide along the slot(s).

Clause 14. The vehicle suspension system of Clause 1, wherein the control arm is connected to the frame portion via a nut and bolt assembly, the bolt extending through the first end of the control arm and through a slot defined in the frame portion, and wherein the retaining device comprises a plate arranged flush with the frame portion, the plate having an aperture through which the bolt extends, and the plate further comprising a slot extending substantially parallel to the slot defined in the frame portion, wherein the plate is clamped to the frame portion via one or more fasteners located in the slot in the plate.

Clause 15. The vehicle suspension system of Clause 1, wherein the suspension system is for a front wheel of the vehicle.

Clause 16. The vehicle suspension system of Clause 15, wherein the control arm is a front lower control arm.

Clause 17. The vehicle suspension system of Clause 1, wherein the suspension system is a multilink suspension system and the control arm is a compression arm.

Clause 18. A vehicle comprising the suspension system of Clause 1.

Claims

CLAIMS1. A vehicle suspension system comprising a control arm mounted at a first end to a frame portion of a vehicle, wherein at least a portion of the control arm is arranged to slide relative to the frame portion when the control arm is subjected to loads exceeding a predetermined level, the system further comprising retaining means configured to prevent the control arm from sliding relative to the frame portion when the control arm is subjected to loads below the predetermined level.
2. The vehicle suspension system of Claim 1, wherein the suspension system is configured such that sliding motion of the control arm causes an angular displacement of a steering wheel of the vehicle.
3. The vehicle suspension system of Claim 1 or Claim 2, wherein a second end of the control arm is mounted directly or indirectly to a knuckle, and the control arm is configured to slide relative to the frame portion in a sliding direction generally parallel to an axis defined by a straight line extending between the first and second ends of the control arm.
4. The vehicle suspension system of any preceding claim, wherein the first end of the control arm is slidably mounted to the frame portion of the vehicle.
5. The vehicle suspension system of any preceding claim, wherein the first end of the control arm is pivotally connected to the frame portion such that the control arm is able to pivot relative to the frame portion about a pivot axis.
6. The vehicle suspension system of Claim 5, wherein sliding motion between the control arm and the frame portion causes displacement of the pivot axis in a sliding direction.
7. The vehicle suspension system of any preceding claim, wherein the frame portion comprises a slot through which the first end of the control arm is connected to the frame portion and wherein the control arm is arranged to slide along the slot when subjected to a load exceeding the predetermined level.
8. The vehicle suspension system of Claim 7, wherein the frame portion comprises a pair of opposed slots and the first end of the control arm is connected between the pair of slots and is slidable along the pair of slots when subjected to a load exceeding the predetermined level.
9. The vehicle suspension system of Claim 8, wherein the frame portion is a clevis and the slots are provided respectively in mutually-opposed side walls of the clevis.
10. The vehicle suspension system of any preceding claim, wherein the retaining means exerts a clamping force between the control arm and the frame portion, the clamping force being sufficient to prevent the control arm from sliding relative to the frame portion when the control arm is subjected to loads below the predetermined level, and the clamping force being insufficient to prevent the control arm from sliding relative to the frame when the control arm is subjected to loads exceeding the predetermined level.
11. The vehicle suspension system of any preceding claim, wherein the retaining means comprises a nut and bolt assembly.
12. The vehicle suspension system of Claim II, wherein the retaining means comprises a deformable component configured to deform when the control arm is subjected to loads above the predetermined level.
13. The vehicle suspension system of Claim 12, wherein the control arm is connected to the frame portion via a nut and bolt assembly, the bolt extending through the first end of the control arm and through a slot defined in the frame portion, and wherein the retaining means comprises a washer having a tab extending from its periphery, the tab being bent and engaging a locating feature defined in the frame portion adjacent the slot, and wherein the tab is configured to straighten when the control arm is subjected to loads exceeding the predetermined level thereby permitUng the control arm to slide along the slot(s).
14. The vehicle suspension system of any of Claims 1 to 11, wherein the control arm is connected to the frame portion via a nut and bolt assembly, the bolt extending through the first end of the control arm and through a slot defined in the frame portion, and wherein the retaining means comprises a plate arranged flush with the frame portion, the plate having an aperture through which the bolt extends, and the plate further comprising a slot extending substantially parallel to the sot defined in the frame portion, wherein the plate is clamped to the frame portion via one or more fasteners located in the slot in the plate.
15. The vehicle suspension system of any preceding claim wherein the suspension system is for a front wheel of the vehicle.
16. The vehicle suspension system of Claim 15, wherein the control arm is a front lower control arm.
17. The vehicle suspension system of any preceding claim, wherein the suspension system is a multilink suspension system and the control arm is a compression arm.
18. A vehicle comprising the suspension system of any preceding claim.
19. A vehicle suspension system substantially as herein described with reference to or as shown in any of the accompanying figures.
20. A vehicle substantially as herein described with reference to or as shown in any of the accompanying figures.